Research On Optimal Design And Performance Analysis Of Electromagnetic Active Suspension For EV With Four-Wheel Independent Drive

With the rapid development of automobile industry, humankind is faced with the challenges of energy and environment. Electric vehicle is regarded as the best choice to achieve sustainable transportation development, and EV with 4IDW has been considered as the last drive layout of electric vehicle. However, Owing to its special power structure distribution, the unspring mass has been increased, which causes decline of ride comfort and handling stability. The ride comfort and handling stability of vehicle is affected by suspension system direct ly. Active suspension system can provide active force to ensure suspension performance is optimal under various driving conditions, and electromagnetic active suspension with high response speed, simple structure and high control precision is preferred actuator for active suspension system. Based on the drive wheel of a electric vehicle, an electromagnetic active suspension actuator has been designed which has preferably dynamic characteristics, compact size and steady electromagnetic force. Based on the structure parameters of actuator and theoretical model, The optimal design theories and methods of electromagnetic active suspension actuator has been explored by applying sensitivity analysis and multi-objective Particle Swarm Optimization(PSO). The main contents are as followed:(1) Based on the design requirement of drive wheel, permanent magnet synchronous linear(PMSLM) with Halbach array has been selected as the actuator of electromagnetic active suspension. Based on the design criteria of motor and the characteristic of PMSLM, the design scheme of electromagnetic active suspension has been study, and the initial structure design parameters has been achieved, which are the bases of subsequent analysis for electromagnetic actuator.(2) Using the vectorial formulation of magnetic flux, theoretical analysis quantitative of actuator has been built by solving differential equations and Bessel functions, and the model validation of theoretical analysis and FEA has been done by ANSOFT. Major structural parameters of actuator have been achieved by the method of Morris local sensitivity analysis, which is the basis of optimization for actuator.(3)Using multi-objective Particle Swarm Optimization and taking structural parameters of actuator as design variables to optimize dynamic characteristic and loss, the multi-objective optimization of electromagnetic has been done and optimal Pareto set has been achieved. Based on fuzzy set theory, the optimal structure parameters have been achieved. The results show after optimization the coefficient of copper loss decreases 20.1%, the coefficient of thrust per volume increases 8.1%, thrust ripple decreases 56.1%.(4)Based on the characteristics of electromagnetic liner actuator, the mechanism of thrust ripple has been study. The effective measure to decrease thrust ripple has been proposed by analytic analysis of cogging force and end force. The results prove the force ripple can be decrease to 2.4% with 2.8mm thickness of telos for the optimal actuator.